The invention relates to a method of forming a package-like back-to-back wafer batch (BTB wafer batch) to be positioned in a process boat, the back-to-back wafer batch consisting of a predetermined even number of wafers disposed in rows, such as solar wafers, to be doped on one side, with each side that is not to be doped abutting congruently the side not to be doped of the respective adjacent wafer, wherein the first and the second half of the predetermined even number of wafers is provided in a standby position in each case by means of a carrier, which is clamped in a horizontal plane with upward facing stacking slots, and moved out of the carrier in succession in the form of a first and a second wafer stack, respectively by means of lifting combs that can travel vertically and are each positioned beneath the carrier, and positioned in succession in a combined lifting position, in which the wafers of the first wafer stack and the second wafer stack are each offset by 180° with respect to one another and aligned to one another and the second wafer stack is joined together with the first wafer stack by positive locking to produce the package-like back-to-back wafer batch (BTB wafer batch), by simultaneously and congruently joining together the sides not to be doped of the wafers of the first and the second wafer stack associated to one another, whereupon the BTB wafer batch is picked up in positively locked form by a transfer gripper and deposited at an insertion position in the process boat.
The invention further relates to a method for forming a package-like back-to-back wafer batch (BTB wafer batch) to be positioned in a process boat, the back-to-back wafer batch consisting of a predetermined even number of wafers disposed in rows, such as solar wafers, to be doped on one side, with each side which is not to be doped abutting congruently the side not to be doped of the respective adjacent wafer, wherein the predetermined number of wafers to be doped on one side is provided in rows in the stacking slots of a carrier, which is clamped in a horizontal plane with upward facing stacking slots, half of the predetermined even number of wafers for the BTB wafer batch to be formed is moved from the carrier and transferred in the form of a first wafer stack by means of a transfer mechanism to the process boat and positioned in an insertion position in its stacking slots, then the other half of the predetermined number of wafers for the BTB wafer batch to be formed is moved from the carrier and transferred by the transfer mechanism to the process boat in the form of a second wafer stack, the wafers of which have previously been offset by 180° with respect to the position of the wafers of the first wafer stack in the insertion position of the process boat, positioned above wafers in alignment with the insertion position of the first wafer stack in the process boat, offset from the insertion position by a distance at least as great as the wafer thickness, and then joined together with the first wafer stack in the insertion position of the process boat, with the sides not to be doped of the wafers of the first and the second wafer stack associated with each other being placed together simultaneously and congruently.
The invention further relates to a handling system for loading a process boat with several insertion positions with wafer batches before doping in a diffusion furnace, with an automatic transfer system by which a carrier fitted with a predetermined even number of wafers can be moved along a horizontal transport plane into a standby position for forming wafer stacks, with a clamping module, from which the carrier must be held aligned with upward facing stacking slots in the standby position, so that the centres of the wafers in the stacking slots of the carrier are precisely aligned with the comb holes of lifting combs that can be moved vertically of a first and a second vertical axis module, which are each rigidly disposed beneath the clamping module in the standby position, wherein the first half of the predetermined number of wafers in the carrier held by the clamping module is moved by the lifting comb of the first vertical axis module as the first wafer stack upwards into a first lifting position and is to be provided here by means of a rotating mechanism in a position offset by 180° with respect to its standby position in the lifting comb of the first vertical axis module and the lifting comb is lowered again, after which the second half of the number of wafers located in the stacking slots of the carrier is lifted into a second lifting position by the lifting comb of the second vertical axis module, then the second wafer stack is moved without rotation into the first lifting position above the first wafer stack, into which the first wafer stack is raised by the lifting comb of the first vertical axis module and inserted in the second wafer stack and the wafers of the first and the second wafer are placed together back-to-back forming a packet-like BTB wafer batch with a doubled doping surface in the lifting comb, and with a transfer gripper, by which the formed BTB wafer batch is moved from the first lifting position to the process boat and deposited at one of the insertion positions.
A handling system for loading and unloading of a process installation with at least one carrier loadable and unloadable with at least one flat substrate for a vertical transport of the substrate, and a method for operating this handling system are principally known from e.g. DE 10 2004 039 787. According to this a first and a second handling module are provided, whereby at least one substrate handling unit is associated with at least one of the handling modules for a substrate transfer separate from the carrier. The carrier is transferable with the vertically aligned substrate between the process installation and the first handling module, the process installation and the second handling module and between both of the handling modules, and the substrate handling unit is designed as a multi-axis robot, preferably with one or more vacuum grippers.
A handling device for the bulk transfer of semiconductor wafers from container to container for processing in the back-to-back configuration is known from U.S. Pat. No. 4,856,957 A. The handling device includes a stage for selectively raising the wafers from a boat upward into a retaining mechanism. The wafers are confined in a back-to-back configuration through a slot in the end of a back-to-back retainer. The back-to-back configured wafers are then removed, processed and then disposed back in the retainer mechanism.
A handling device for automatically transfers semiconductor wafers between plastic wafer boats and closed bottom quartz boats is also known from U.S. Pat. No. 4,840,530 A. The handling device has a wafer elevator for elevating the wafers in a plastic boat to a position where the wafers can be retained by first and second retainer walls. The retainer walls are pivotable relative to one another between open and closed positions. The handling device includes also a turntable that is rotatable over 180 degrees about a vertical axis. In transferring wafers from the plastic boat to the quartz boat the retainer walls pick up one half of the wafers in the plastic boat. The plastic boat is then rotated 180 degrees by rotating the turntable. This reorients the wafers remaining in the plastic boat for back-to-back placement into the quartz boat.
A handling device for bringing two wafers to the state of back adhesion and shifting them to a boat is further known from JP 63 84043 A. This handling device comprises a table on which a plurality of cassettes are placed in which wafers arranged in the forward direction are housed. When the table is moved to a predetermined position, wafer supports for a rotary means are passed through holes in the table and holes in the cassettes and elevated. Thus the wafers are lifted to the upper sections of the cassettes and the directions thereof are changed at 180 degrees. Then the wafers are lowered, thus re-housing the wafers into the cassettes under the state in which they are disposed in the opposite direction. When a base is shifted onto the cassettes in which the wafers in the forward direction are stored, the rotary means transfer the wafers in the forward direction to a holding means in the base. When the base is moved onto the cassettes in which the wafers in the opposite direction are housed, the rotary means insert the wafers in the opposite direction among wafers in the forward direction in the base. An adhesion means in the base fast sticks the wafers back to back, and the wafers are stored in a boat.
For the increase of the efficiency of the production processes of solar cells the automation and acceleration of solar wafer handling, specifically the load and unload process of the process boat by which the solar wafers have to be delivered in and out of the diffusion oven, respectively, is an important factor. The diffusion process requires only the diffusion of one side of the wafer. The solar wafers are fed to the diffusion oven in a process boat typically provided with 200 slots inclined by 3° to the vertical. Such an incline effects a pre-alignment of the solar wafers so that they rest against the flanks of the process boat.